The deal signals the start of an effort by Pfizer to enter the business of selling ultra-expensive drugs for ultra-rare diseases, a market that big pharmaceutical companies once largely ignored.

And the move will put the company into direct competition with Genzyme, the biotechnology company that already sells a drug called Cerezyme to treat Gaucher disease.

Genzyme has been struggling to recover from a severe shortage of Cerezyme brought about by manufacturing problems.

Pfizer will pay Protalix $60 million initially and up to $55 million later. The companies will split expenses to market the drug and the revenue from its sales on a 60-40 basis, with Pfizer having the larger share.

Protalix is close to filing its application for federal approval of the drug. The product, called taliglucerase alfa, could reach the market next year.

Although analysts viewed the deal as a validation of Protalix’s drug and its novel manufacturing process, shares of Protalix fell nearly 14 percent, to $8.51, apparently because investors were disappointed that Pfizer did not acquire the company. Pfizer’s shares rose nearly 4 percent, to $18.85.

Protalix makes proteins that serve as drugs in genetically engineered carrot cells that grow inside plastic bags. That is far less costly, it says, than the process used by most biotechnology companies, including Genzyme, which is to use genetically engineered hamster ovary cells growing in stainless steel tanks.

That will probably mean that Protalix’s taliglucerase will be cheaper than Cerezyme, though executives at Pfizer and Protalix declined to discuss the price on Tuesday.

Big pharmaceutical companies once tended to disregard rare diseases, preferring to develop blockbusters for common ailments like diabetes and high cholesterol. But with sales growth slowing and older blockbusters losing patent protection, the companies have become more willing, even eager, to sell specialized drugs.

“This is the first step in the pursuit of a formal strategy around orphan drugs and rare diseases,” David Simmons, president of Pfizer’s established products business unit, said in an interview.

While there might be few patients with each disease, he said, “collectively, it’s a very large patient population with a great unmet medical need.”

Besides, Genzyme has proved that even a drug for a rare disease can generate big sales if the price of the drug is high enough. Only about 5,700 people in the world are being treated with Cerezyme. But since the drug costs about $200,000 a patient each year, sales exceeded $1 billion last year.

Pfizer is not alone in pursuing treatments for rare diseases. In October, GlaxoSmithKline announced a deal with Prosensa, a Dutch company, to develop drugs for Duchenne muscular dystrophy. And in June, Novartis won approval from the Food and Drug Administration to sell its drug Ilaris as a treatment for cryopyrin-associated periodic syndrome. Only about 300 Americans suffer from that syndrome, an inflammatory condition caused by a gene mutation.

Philip Nadeau, an analyst at Cowen & Company, called the entrance of Pfizer as a competitor a “modest negative” for Genzyme. However, Mr. Nadeau said, “even Pfizer’s marketing prowess is unlikely to relieve” safety concerns some doctors have about the Protalix drug. The main concern is that because it is produced in plant cells, taliglucerase may spur immune reactions in some patients.

Genzyme’s stock rose a bit less than 1 percent, to $51.11. The company announced Monday that it had resumed shipping some newly manufactured Cerezyme. Manufacturing had been shut down in June after a virus contaminated the company’s factory in Boston.

The shortfall left Genzyme vulnerable to Protalix and also to Shire, a British drug company that is also developing a drug for Gaucher disease. Because of the shortage, the Food and Drug Administration has been allowing some patients to use the Shire and Protalix drugs even though they have not been approved.

Gaucher disease is an enzyme deficiency that can cause an enlarged liver and spleen, anemia, frequent bleeding and bone weakness. All three drugs consist of the enzyme that people with Gaucher disease are missing.

About IPPF

The International Pemphigus & Pemphigoid Foundation’s most important objectives are to provide patients and doctors worldwide with information about pemphigus and pemphigoid, and to provide patients and their caregivers much needed comfort and support so they can continue to live active, productive lives.Read more »